A millivoltmeter of millivolt range is to be converted into an ammeter of -ampere range. The value (in ohm) of the necessary shunt will be:
Step 1. Given data:
Range of millivoltmeter = millivolt = Volt
The expected range of ammeter ampere
Step 2. Calculating the value of shunt resistance
For making an ammeter, shunt resistance is connected in parallel to the galvanometer.
Here, shunt resistance= , = galvanometer voltage, = full-scale deflection current,
Hence , Where subscript g refers to the galvanometer,
Here voltmeter's resistance =
Now Because in an ideal voltmeter,
Thus, from ,
Thus, the correct option is option D.